Anchor type fasteners for attaching, mounting, or securing various objects or devices to masonry structures are of course well known in the art. Prior art fasteners of the aforenoted type usually, for example, comprised one of two types, that is, anchors having expansion structure incorporated therein for expansibly engaging the interior peripheral sidewall of a bore pre-drilled into the masonry structure, or anchors utilizing bonding materials for adhesively bonding to the interior peripheral sidewall of the pre-drilled bore. While both of these types of anchors have of course been operationally satisfactory from the viewpoint of being able to mount, attach, or secure various objects or devices to the masonry structure once such fasteners have themselves been mounted or secured within the bores pre-drilled within the masonry structure, both of such types of anchors are somewhat difficult and time-consuming to install, as well as to remove from the masonry structure if so desired.
In order to overcome the aforenoted operational drawbacks, disadvantages, and deficiencies characteristic of such known PRIOR ART masonry anchors, an improved, one-piece masonry anchor of the type disclosed within U.S. Pat. No. 3,937,119, which issued to Ernst on Feb. 10, 1976, was developed. More particularly, as disclosed within the noted patent, such PRIOR ART anchor, as illustrated in FIGS. 1 and 2 of the present patent application drawings, which respectively correspond to FIGS. 5 and 3 of the noted patent, comprises an anchor 10 having a head portion 12, an elongated shank portion 16, and a pointed tip or extremity 18. A tapered helical thread 20 is provided upon the elongated shank portion 16, and a constant diameter helical protuberance or secondary thread 22 is also provided upon the elongated shank portion 16 such that the convolutions of the protuberance or secondary thread 22 are interposed between the convolutions of the helical thread 20, both sets of threads having the same pitch with root portions 24 defined between adjacent convolutions. The helical protuberance or secondary thread 22 is provided so as to radially center the anchor 10 within a bore 30 pre-drilled within masonry structure 28. When the anchor 10 is secured within the bore 30, it serves to attach or mount a workpiece or the like 32 upon the masonry structure 28.
As shown in connection with the embodiment of FIG. 1, which corresponds to FIG. 5 of the noted patent, a reaming or sizing section 40 may be provided upon the anchor 10 so as to accurately prepare or size the diameter of the bore 30 so as to effectively conform with the diametrical dimension of the centering or guide means as defined by the protuberance or secondary thread 22. A unique feature of this anchor also comprises the provision of notched regions 26 within the primary helical thread 20 of the anchor 10 so as to permit dust or aggregate particles gradually removed from the sidewall portions of the masonry structure 28 to migrate and accumulate within reservoirs 34, defined between adjacent convolutions of the primary and secondary threads 20,22, in order to effectively reduce torsional friction whereby the anchor device can be inserted into the masonry structure at relatively low torque levels. It is noted, however, that the reaming or sizing section 40 is not provided with any migratory or reservoir structure. It has therefore been experienced that when utilizing a reaming or sizing section or member upon a masonry anchor, of a type similar to that disclosed within U.S. Pat. No. 3,937,119, such dust or aggregate particles dislodged from the sidewall portions of the masonry structure during such reaming or sizing operation cannot, or are not able to, migrate to a suitable reservoir because they are in effect trapped within the plurality of spaces defined between adjacent ones of the axially extending or longitudinal splines defined upon the reaming or sizing section 40, as well as between the plurality of splines and the sidewall of the masonry bore 30. Accordingly, a considerable amount of torsional friction is developed during the insertion of such anchor into the masonry structure which results in the facts that the anchors can only be inserted into the masonry structure with relatively high torque levels, that the anchors sometimes cannot be fully inserted at all, or that the required application torque is so high that the fastener head becomes separated from the fastener shank.
A need therefore exists in the art for the development of a self-tapping masonry anchor, which may also utilize a reaming or sizing member or section, wherein dust or aggregate particles generated during the self-tapping, reaming, or sizing operations are accommodated so as to effectively reduce the torsional friction whereby the anchor device can be easily inserted into the masonry structure at relatively low torque levels.